A group of Caribbean countries have agreed to back Buenos Aires and block any ships flying the Falklands flag from docking in their ports, Argentina's foreign minister Hector Timerman has said.
They include the Commonwealth countries of Antigua-Barbuda and St Vincent-Grenadines, along with Cuba, Nicaragua and Dominica, Timerman said.
Argentina received strong support for its blockade at a meeting in Venezuela of a left-leaning bloc of South American and Caribbean nations.
The Ecuadorian president, Rafael Correa, said: "It is time for Latin America to decide sanctions against this mistaken power that pretends to be imperialist and colonialist in the 21st century.
"I think we have to apply more forceful things. We have to talk about sanctions."
Argentina hopes that diplomatic and economic measures will pressure Britain to comply with UN resolutions encouraging both countries to negotiate the islands' sovereignty. Britain has refused so far.
Hugo Chávez, the president of Venezuela, said: "If it should occur to the British empire to attack Argentina militarily, Argentina won't be alone this time.
"Venezuela is no power, but we've got some weapons and the will to face any imperialist aggression."
Tensions have risen as the 30th anniversary of Argentina's invasion nears